Line stopper shell cutter



Dec. 15, 1953 F. H. MUELLER 2,662,428

LINE STOPPER SHELL CUTTER Filed July 51, 1951 INVENTOR FRANK H. MUELLER BY r W.

ATTORNEY Patented Dec. 15, 1953 LINE STOPPER SHELL CUTTER Frank H. Mueller, Decatur, IIL, assignor to Mueller (30., Decatur, 111., a corporation of Illinois 1 Application July 31, 1951, Serial No. 239,595

2 Claims. (01. 77-69) This invention relates to shell cutters and more particularly to an improved shell cutter espeially adapted for cutting pipe lines and for retaining, and removing with the cutter, the coupon cut out from the pipe line by the cutter.

Shell cutters are boring tools of an annular construction in the form of a hollow cylindrical shell having an annular cutting edge which cuts away only an outer concentric ring portion of the material. The disc-like central or intermediate portion thus cut out is conventionally termed a coupon. Conventional shell cutters are usually provided with a central threaded pilot bit or drill, the function of which is to both center the cutter and retain the coupon cut out thereby so that such coupon may be withdrawn from the hole. This latter function is particularly important in pipe lines. With the conventional pilot bit type of cutter, however, diificulty is frequently had in removing coupons from the pipe. The ordinary cutter, when emerging through the inner wall of the pipe, usually will fracture the coupon off along forwardly flaring lines, thus giving the coupon a ragged rim, slightly larger than the hole which is cut. Hence, when the shell cutter is withdrawn, the coupon is often pulled off the pilot bit and falls into the main or pipe being cut. The disadvantages attendant with such loss of the coupon are obvious, particularly when the main is in service.

fence, it is an object of this invention to provide an improved shell cutter which will positively retain and withdraw the coupon with the cutter.

It is another object of this invention to provide an improved shell cutter in which the coupon formed thereby has a diameter at least small enoughto pass through the hole ultimately made by the cutter.

It is a further object of this invention to provide an improved shell cutter of simple and inexpensive construction which will accomplish the above objects.

Other objects and advantages of the invention will be apparent from the following description and accompanying drawings, in which:

Figure 1 is a side elevational view of a shell cutter embodying this invention.

Figure 2 is a longitudinal sectional view of the shell cutter shown in Figure 1.

Figure 3 is an end view of the shell cutter shown in Figure 1, taken from the toothed end.

Figure i is a diagrammatic view of the operation of a shell cutter embodying this invention,

and

Figure 5 is a diagrammatic view of the operation of a conventional shell cutter.

Referring now to the drawings, there is shown in Figure l a shell cutter ll] embodying this invention. The cutter comprises a hollow cylindrical shell l2 having means at the rearward end thereof, such as the inner threads I4, for attaching the cutter to a boring bar (not shown) for rotation thereby. The other end of the shell 12 is provided with a plurality, nine as shown in the drawings, of axially extending integral cutting teeth [6. Preferably the diameter of the shell 12 tapers slightly rearwardly. The front of each tooth (i. e., with reference to its direction of rotation) is provided with a substantially plane radial cutting surface it, while the forward end of each tooth has a surface 28 that is inclined rearwardly of the direction of tooth movement. The intersection of these two surfaces form a cutting edge described in greater detail hereinafter.

The outer forward end edge of eachtooth l6 v.is recessed,.as at 22. 'This recess divides the cuttingedge of each tooth into two .parts one, an advance inner. cutting edge 24 and, two, a following outer, cutting edge 26. It will be noted that the following cutting edge 26 is much shorter than the advance cutting edge 26.

Although the cutting surface N3 of each tooth I6 is shown in the drawings as being a plane radially disposed surface, it will be understood that this surface need not be plane nor disposed exactly radially of the cutter but, instead, may be curved and/or arranged at. an angle to a radius extending through such surface. Likewise, the cutting edges 24 and 26 need not be straight. It is essential, however, that the advance and following cutting edges 24 and 26, respectively, be oifsetboth. radiallyand axially as shown. Preferably, during the manufacturing process, the teeth It are hardened and have the hardness of their roots subsequently drawn to provide a spring temper thereto.

The intermediate section of the shell l2, between the teeth IG and the attaching threads M, preferably is provided with several circumferential series of holes 28 to permit adequate lubrication of the cutter and for permitting the passage of fluid therethrough when cutting a pipe line that is in service.

In use, the inner annularly arranged series of cutting edges 24 acts in advance and, when these cutting edges have out almost entirely through the wall 30 of a pipe, the coupon 32 may fracture off along the forwardly flaring ragged edges 34 3 indicated in Figure 4 of the drawings. This fracturing off of the coupon 32 before the out has been completed causes the diameter of the coupon to be somewhat greater than that of the cut made by the annularly arranged series of advance cutting edges. It will be note d, however, that the lines of fracture 34 do not extend radially outwardly beyond the area to be encountered and cut by the annularly arranged series of follo w ing cutting edges 28. Therefore, this latter series of following cutting edges will rean off-the ragged edge of the opening left by the coupon 32 to provide a smooth walled out having a diameter large;

enough to receive the coupon which has' been" fractured off by the advance cutting edges 24.

In contrast to the operation of, a shell; cutter,

embodying this invention, a conventional shell cutter 35 having a singleseries of cutting edges 3-4} will fracture off a coupon 38 along the ragged edges 40- indicated in Figure 5 of the drawings. It will be noted infthis instance that the lines of fracture 40 extend radially outwardly beyord the diameter ofthe annular cut made by the single series. of cutting edges 39; Hence, the coupon" 38 has a ragged rim of a diameter somewhat greater than that of the circular hole made by the cutter 35 Thiscoupon 3 8 is retainedon the pilot drill 42- of the conventional cutter but is frequently pulled off ofthe same when withdrawing thecutter from the main upon completion. of the boring operation.

In order to retain the coupon 32 cut from the pipe bythe improved cutter Hi and to provide pilot drill is required. A pilot drill supplies some guiding of the cutter during the cutting operation, but the principal function of such pilot drill in conventional main-boring cutters is to retain the removed coupon for Withdrawal with the cutter. It may be necessary, however, to employ a pilot; drill with the larger sizes; of the improved cutter ill in order to steady the same in use.

It will be realized that the specific embodiment a of the invention described is for the purpose of illustrating: the principles of the invention and that various changes may be made by one skilled in the art while. retaining these same principles. Therefore, this invention includes all modifications and embodiments which are encompassed by t he spirit andscope of the following claims.

I claim:

1 In a shell cutter for making an annular cut through the side wall of a pipe line so that removah of the. resulting coupon leaves a circular aperture, the. cutter-h v ng, an annular serie of axiallyextending teeth. each provided; with; inner and, outer curved surfaces and a somewhatrearwardly. inclined end; surface, the combination of means defining. a, step, at the outeredge of" the n 'rface ofea h tQ thtQ fqrmi ner nd; Q l

cutting. edgesv thereon with, said outercutting edge. being, offset. rearwardly of said, inner cuttin edgeiwith. reference t0- the direction of feed of 30 the. cutter, theilength of; saidouter cutting'edge some means for withdrawing the same from. the

hole, the inside of the shell. I2, adjacent its forward end, isprovided with tapping threads 44. on the inner side of each tooth l6. Thesethreads 44 serve to tap and securely grip the coupon. 32; so

that? after the hole has been out through the pipe the coupon will be withdrawn simultaneously withthe cutter l0. Preferably, thesethreads 44 have the same pitch as the rate of automatic feedperrevolution of the cutter. In this connection 'it i's pointed. out that shell cutters of this type, particularly when cutting holes intofor through a pipe line, are normally used with a drilling machine. having an automatic feed. Hence, aspreviousl-y stated, the tapping threads 44.:have;the-Isamepitch. as. therate of feed per revolution ofthe automatic feed device incorporated in the drilling machine. It has been found. in actual practice that these threads 44 gripthecoupon 32. so tightly that it is evensomewhat difiicult to. remove the coupon. from. the cutter H1 after the cutter has been. withdrawn from theipipe.

It: has also been found. that in the smaller forms of theimproved cutter described. above no being less thanthelength. of said inner cutting edge, whereby if: the. coupon fractures off; alon forwardly flaring surfaces when: the cutter has nearly completedanv annular-cutthrough theside a. walLo'f-a pipe line, the fracture surfaces will egrfief erenee s cited in the file of this patent STATES PATENTS Name. t

-..-r-7--1-.-.-"1"-- 9 W ne. my 6.191s 1,743,338 Field Jan. 14,1930 

